A continuous supply of high purity feed gas is required in semiconductor manufacturing, analytical instrumentation, the operation of fuel cells, and other applications in which impurities in the feed gas can result in defective products, incorrect measurements, and damage to expensive equipment. For example, chemical vapor deposition processes are highly sensitive to small amounts of impurities in the feed gases used and are totally dependent on an uninterrupted supply of high purity feed gas. Many sensitive analytical instruments require a reliable supply of high purity reference or purge gases in order to generate reliable analyses. Fuel cells that operate on hydrogen can be irreversibly damaged by impurities such as hydrogen sulfide and carbon monoxide when present in the hydrogen feed gas.
High purity gases for such applications may be provided from various types of storage systems or alternatively may be generated immediately prior to use. The operation of storage systems may be susceptible to contamination, for example, when discharged tanks or cylinders are refilled from an external source or are replaced with full tanks or cylinders. The operation of high purity gas generating systems may be subject to operational upsets or contaminated feedstocks, which may introduce undesirable contaminants into the high purity gas product.
One approach to this problem is to shut down the gas-consuming process when impurities in the high purity or ultra-high purity feed gas are detected at a concentrations above allowable limits. This action reduces the potential for defective products and damage to sensitive equipment, but requires downtime to correct the problem and restart the process. Another approach is to provide a purification system or guard bed that operates continuously on the feed gas or is used to purify the feed gas stream only when contamination is detected in the feed gas.
It would be desirable to reduce the concentration of damaging contaminants in a high purity feed gas without interruption of the downstream process and without the need to purify the entire feed gas stream. The embodiments of the present invention address this need as disclosed in the following specification and defined by the claims that follow.